medium importancemedium difficulty6 min

Electric Motor

An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.

In one line: Motor means current becomes motion.

Practice This Concept

Understand it

When current flows through the coil of a motor placed in a magnetic field, forces act on the two sides of the coil in opposite directions.
These forces create a turning effect, so the coil rotates.
The split-ring commutator helps keep the coil rotating in the same direction.
Motors are used in fans, mixers, washing machines, and many other appliances.

Example

A ceiling fan works because an electric motor rotates its blades when current passes through the coil system inside it.

Formula and rule

Motor action depends on force on a current-carrying conductor in a magnetic field, explained by Fleming's left hand rule.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

1If a small motor coil is connected to a battery, one side of the coil moves upward and the other downward due to magnetic force.
2After half a turn, the commutator reverses current so the coil keeps turning.

Method you can reuse

1Place a coil between magnet poles.
2Pass current through the coil.
3Forces act on opposite sides of the coil.
4Coil rotates.
5Commutator reverses current every half turn to keep rotation going.

Sketch it in your answer

Draw a rectangular coil between magnet poles, split-ring commutator, brushes, and battery connections with rotation arrows.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

Why does the coil in an electric motor keep rotating instead of stopping after one push?

Think first, then show answer

The split-ring commutator reverses the current after every half turn, so the force on the coil keeps producing rotation in the same direction. This is why the motor continues to spin.

Common wrong answer

The coil rotates because it is simply heated or pushed by the battery.

Why it loses marks: The real cause is magnetic force on current-carrying sides of the coil.

Don't mix this up

Students often say the motor itself produces electricity. In fact, it uses electricity to produce motion.

Exam tip

In answers, mention the rotating coil, magnetic field, and commutator together for full marks.

Electric Motor diagram

Open full screen to read every label clearly.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Explain working of an electric motor, label its parts, or state the role of the commutator.

1
Enough for 1 mark
An electric motor is a device that converts electrical energy into mechanical energy by using the force on a current-carrying coil in a magnetic field.
2
Add for 2 marks
Example: A ceiling fan works because an electric motor rotates its blades when current passes through the coil system inside it.
3
Add for 3 marks
When current flows through the coil of a motor placed in a magnetic field, forces act on the two sides of the coil in opposite directions.

MCQ Quiz

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